Optimizing M30 Concrete Mix Design: A Step-by-Step Approach for Achieving Desired Strength

M30 Concrete Ratio

The M30 concrete mix ratio is a proportion of ingredients used to achieve a particular strength in concrete. The ratio is 1:0.75:1.5, which means for every 1 part cement, you need 0.75 parts sand and 1.5 parts aggregates when making 1 cubic meter of concrete

Concrete Mix Design IS Code

For Concrete mix design, we use, IS 456, and IS 10262.

Required Data for M30 Grade of Concrete Mix Design

1. Characteristic Compressive Strength: 30 Mpa
2. Maximum Size of Aggregate: 20 mm
3. Work-ability, Slump: 125 – 150 mm
4. Degree of Quality Control: Good
5. Type of Exposure as per MORTH Table – 1700-2: Severe
6. Minimum Target Mean Strength as per MORTH Table: 1700-8: 42 Mpa ( 30 + 12 )
7. Max. Water Cement Ratio as per MORTH Clause – 1715.2: 0.4
8. Minimum Cement Content as per MORTH Clause – 1715.2: 360 Kgs
9. Maximum Cement Content as per MORTH Clause – 1715.2: 450 Kgs

Required Test Data for Materials for M30 Grade of Concrete Mix Design

Specific Gravity details :

Type of Cement: OPC 53 Grade

Water Absorption details:

The calculation for Target Mean Strength

Target Mean Strength for M30 Grade of Concrete Mix Design as per MORTH Table 1700-8 specification ( 5th revision )

For M30: 12 Mpa

Target mean strength f’ck= fck + kσ

1. fck = characteristic strength below which certain percentage of test results are expected to fall.
2. k = Himsworth constant for 5% risk factor is 1.65.
3. σ = Standard deviation is 5.0 M30 (from table 8 of IS:456-2000)
4. Target mean strength f’ck= 30 + 1.65×5 = 38.25MPa

Selection of Water Cement Ratio for M30 Grade of Concrete Mix design

1. Maximum Water Cement Ratio Permitted As per MORTH Clause – 1715.2: 0.40
2. W/c Ratio Selected As 0.39

Selection of Water for M30 Grade of Concrete Mix Design 

Water Content as per Table 2, of IS: 10262:2009 for 20 mm maximum size of aggregate IS: 186 litres.

The above-estimated water is suggested for a slump range of 25 to 50 mm in the above mentioned IS code. For each 25 mm increase in a slump 3% water can be increased as per clause No. 4.2 IS 10262: 2009

The required slump is 150 mm, so

1. For 50 mm slump water required = 186 liter
2. For 75 mm slump = 186 x 3% = 5.58 ltr
3. 186 + 5.58 = 191.58 ltr.
4. For 100 mm slump = 186 x 6% = 11.16 ltr
5. 186 + 11.16 = 197.16 ltr
6. For 125 mm slump = 186 x 9% = 16.74 ltr
7. 186 + 16.74 = 202.74 ltr
8. For 150 mm slump = 186 x 12% = 22.32 ltr
9. 186 + 22.32 = 208.32 ltr.

Hence water requirement calculated as 208.32 ltr.

Superplasticizer is used in the mix. The water content can be reduced up to 35 Percent and above as per IS: 10262 – 2009 Based on trials with Superplasticizer water content reduction of 21.51 percent has been achieved with the same dose.

Water required for M30 Concrete: 140.0

Say 140.0

Cement Content

Water Cement Ratio: 0.39

Hence Cement content : 140.0 / 0.40= 350 Kg

Minimum cement content as per MORTH  – 360 kg/cum

Cement Requirement for M 30 Concrete: 360 Kg

Hence Cement Content: 350 Kg

Proportion of Volume of Coarse and Fine Aggregate Content for M30 Grade of Concrete Mix Design

Hence Coarse aggregate content for MSA 20 mm: 60%

Sand content can be adopted, Max. : 40%

Course Aggregate Proportions ( 20 mm : 10 mm ) : 50%

M30 Grade of Concrete Mix Design Calculation Formula

We are describing formula of concrete mix design calculation for M30 Grade of Concrete Mix Design but you can use this formula for any grade of concrete

The formula of Volume of material content = material weight / ( material specific gravity * total volume )

Volume of concrete = 1 Cu.M.

1 Cum = 1000 ltr ( in volume)

Volume calculation for materials:

• Cement Content = 350 / 3.15 x 1000 = 0.111 Cu.M.
• Water Content = 140 / 1.00 x 1000 = 0.140 Cu.M.
• Admixture = 1.80 / 1.17 x 1000 = 0.0015 Cu.M.
• Aggregate = 1- ( cement volume + water volume + admixture volume ) = 1 – ( 0.114 + 0.140 + 0.0015 ) = 0.745 Cu.M.

Now we got a volume of each material for use in concrete.

Now convert material volume into weight.

Convert Volume into Weight for Concrete Mix

This formula can be used for any grade of concrete mix design.

Formula = Material weight = material volume x percentage of total volume x material sp. gravity x total volume.

• Mass of coarse aggregates 20 mm = 0.745 x 0.60 x 0.50 x 2.885 x 1000 = 644.8 Kg. =Say 645 Kg.
• Mass of coarse aggregates 12.5 mm = 0.745 x 0.60 x 0.50 x 2.857 x 1000 = 638.5 kg =Say 639 Kg.
• Mass of fine aggregates = 0.745 x 0.40 x 1.00 x 2.723 x 1000 = 811.5 Kg = Say: 812 Kg

Mix Proportion per CUM. for M30 Grade of Concrete Mix Design

1. Cement: 350 Kg
2. Water: 140 Kg
3. 20 mm: 645 Kg
4. 12.5 mm: 639 Kg
5. Sand: 812 Kg

Dosage of admixture, by the Weight of Cement

0.45% of cement weight: 1.80 Kg

Note:

In moisture correction, Weights of Aggregate and water can be replaced by the weights of the free moisture on Aggregates.

Concrete Mix Design Ratio for M30

M30 mix ratio – 1 : 2.5 : 3.5

Trial Mix:1, (For M30 Grade Concrete Mix Design)

The trail mix is required to define the workability ( slump ), density, compaction, and, most of all, the compressive strength of different concrete grades for various purposes.

We are describing here trial for M30 Grade of Concrete Mix Design, but you can use this trial procedure for any grade of concrete.

In this trial mix, we design the following.

1. Water cement ratio
2. Proportion of cement, coarse aggregate, fine aggregate, water, and admixture ( if required ).
3. Workability ( slump ).
4. Density
5. Compressive strength

Concrete Cube Required for Trial Mix

To check the compressive strength of trial mix concrete, we have to cast at least 12 nos. of cubes.

Total Number of Cubes – 12

You can increase the cube numbers for three3 days,  7 days, or 28 days as per your requirement.

Concrete Quantity Required for Trial Mix

Volume of 1 cube mould = 0.150 x 0.150 x 0.150 = 0.003375 cum.

so concrete quantity for 1 cube = 0.003375 cum.

concrete quantity for 12 cubes = 0.003375 x 12 = 0.0405 cum.

We should take a little more quantity of concrete because it will stick on a trial mix drum and slump test purposes.

so assumed concrete quantity = 0.045 cum.

We should not take more quantity for the concrete trail mix because it doesn’t mix properly.

Calculate the Material Weight for Trial

As we calculated materials weight before for one cum.

1. Cement: 360 Kg
2. Water: 140 Kg
3. 20 mm: 645 Kg
4. 12.5 mm: 639 Kg
5. Sand: 812 Kg
6. Admixture: 1.80 Kg

Now we calculate the quantity of materials for a trail mix.

1. Cement = 360 x 0.045 = 16.2 kg.
2. Water = 140 x 0.045 = 6.3 kg.
3. 20 mm = 645 x 0.045 = 29.03 kg.
4. 12.5 mm = 639 x 0.045 = 28.76 kg.
5. Sand = 812 x 0.045 = 36.54 kg.
6. Admixture = 1.8 x 0.045 = 0.081 kg

Trial Mix Procedure

1. Take the weights of all material as described above.
2. After weighing materials, put coarse aggregates 20 mm and 12.5 mm first in the trial mix drum.
3. Now add fine aggregate ( sand ) in trial mix drum and then add the cement.
4. Mix these materials in the dry condition in a drum for at least 30 seconds.
5. Then add 80 to 90 % of the water in a drum in many parts by adding throughout the mix.
6. Add a bit more water in the mix, where you are going to add admixture.
7. Mix the remaining water with the admixture, then add admixture in a concrete mix where you added a bit more water.
8. It’s because, if the mix is fully coated with water, then it will not absorb admixture in it’s pores, and now admixture will perform his best performance.
9. Finish these steps within two minutes.
10. Check if any dry mix sticked inside the surface of a drum, instantly remove it manually from a surface by using the trowel. Stop the drum mixture for a maximum of 10 seconds for this action and restart it again.
11. Mix it for continuously 5 minutes.
12. Check the workability.
13. This is called an initial slump. Note down.
14. Don’t mix the concrete mix continuously; otherwise, the mix will produce more heat, and it causes a decrease in the slump of concrete mix.
15. Start the mixer at the 5-minute interval for about 1 minute.

Requirement of Workability

As we described, our requirement of a slump is 125 – 150 mm at the site.

You have to check a slump after each 30-minute interval of up to 120 minutes ( 2 hours).

Trial Mix Cube Casting Procedure

1. Cube casting shall be done just after a slump test after 2 hours.
2. Cast the concrete cubes manually for better accuracy, don’t use the plate vibrator.
3. Cast the concrete cubes by the same procedure as we usually cast.
4. Cubes shall be cast in three-layer, and each layer’s thickness is 50 mm nearly.
5. But strokes for each layer shall be between 35 to 45 no more difference for an accurate result.
6. Maintain the temperature of the lab or room where trial cubes are going to be cast at 27 +/- 2-degree centigrade.
7. After casting 12 numbers of trial cubes, place the casted cubes on a plane and firm platform. It should be a vibration-free place.
8. Place cover sheet on top of each casted cubes to prevent water evaporation.
9. Leave it for 24 hours
10. After 24 hours, de-mold the trial cubes and give the identification by a permanent marker. Do not use the nail to write on cubes.
11. Place these trial cubes in the water tank immediately, where water temperature shall be maintained at room temperature 27 +/- 2-degree centigrade.

Compressive Strength of Trial Cubes for M30 Grade of Concrete Mix Design

As we described before, we cast 12 numbers of a cube for compressive strength

3 cubes for 3 days

3 cubes for 7 days

and 6 cubes for 28 days.

1. So after 3 days of casting cubes, take out three cubes from the water tank.
2. Bring these cubes to a compressive testing machine and let it dry. We should test cubes, at least in surface saturated dry conditions.
3. Before the test, the cubes set the rate of loading of the compression testing machine at 5 KN per second.
4. Place the cube carefully in the compression testing machine in the center position.
5. Start the compression testing machine and go to the ultimate load.
6. Note down the ultimate load reading.
7. Same like 3 days, we should test for 7 days and 28 days.

Why Wet Cubes Get lower Strength than Dry Cubes

If cubes are dry more than SSD conditions then, there is a chance to get a little bit more strength.

In wet conditions or SSD conditions, concrete cube’s pores are full of water, and when you compress these cubes in the compressive testing machine, water inside the cube works like hydraulic pressure from inside, and this pressure helps to crack the cube earlier than dry cubes.

Required Compressive Strength for Trial Cubes

As we described before that our target means strength for M30 is 42 Mpa.

But for 3 days and 7 days, we are giving below

1. Minimum compressive strength required in 3 days – 40 % – 17 Mpa
2. Minimum compressive strength required in 7 days –  80 % – 34 Mpa

Trial Mix Result

1.Workability Result

2.Compressive Strength Result 

So as you can see from the result above, we got a good result in 3 days and 7 days, but we didn’t get in 28 days. Average of 28 days strength is ( 41.52 + 41.43 ) / 2 = 41.48 N/mm² .

Which is less than 42 MPa. As we described, as per MORTH 5th revision, our requirement in 28 days for M30 is 42 MPa. So now we are going to decrease the water-cement ratio a bit.

Trial Mix: 2 ( for M30 Grade of Concrete Mix Design)

Previously we selected 0.39 water-cement ratio. Now we will do a trial on 0.38. Definitely, compressive strength will increase while decreasing the water-cement ratio.

So we have to calculate our concrete mix design again on 0.38 water-cement ratio because if you change the water-cement ratio, then materials quantity will change too.

We are describing calculation in short here because we described before. If you are getting any doubt, please scroll above for full details.

Cement Content for M30 Grade of Concrete Mix Design

Water Cement Ratio: 0.38

Hence Cement content : 140.0 / 0.38 = 368.42 Kg

Say: 368 Kg

Hence Cement Content: 368 Kg

The proportion of Coarse and fine aggregate will be the same

Hence Coarse aggregate content for MSA 20 mm: 60%

1. Sand content can be adopted, Max. : 40%
2. Course Aggregate Proportions ( 20 mm : 10 mm ) : 50%

Calculation for Materials Volume

1. Volume of concrete = 1 Cu.M.
2. 1 Cum = 1000 ltr ( in volume)
3. Volume calculation for materials:
4. Cement Content = 368 / 3.15 X 1000 = 0.117 Cu.M.
5. Water Content = 140 / 1.00 X 1000 = 0.140 Cu.M.
6. Admixture = 1.80 / 1.17 X 1000 = 0.0015 Cu.M.
7. Aggregate = 1- ( cement volume + water volume + admixture volume ) = 1 – ( 0.117 + 0.140 + 0.0015 ) = 0.742 Cu.M.

Now we got a volume of each material for use in concrete. Now convert material volume into weight.

Convert Volume into Weight for Concrete Mix

1. Mass of coarse aggregates 20 mm = 0.742 X 0.60 X 0.50 X 2.885 X 1000 = 642.2 Kg, Say 642 Kg.
2. Mass of coarse aggregates 12.5 mm = 0.742 X 0.60 X 0.50 X 2.857 X 1000 = 636 kg, Say 636 Kg.
3. Mass of fine aggregates = 0.742 X 0.40 X 1.00 X 2.723 X 1000 = 808.2 Kg, Say: 808 Kg

Mix Proportion per CUM. of M30 Grade of Concrete Mix Design

1. Cement: 368 Kg
2. Water: 140 Kg
3. 20 mm: 642 Kg
4. 12.5 mm: 636 Kg
5. Sand: 808 Kg

Dosage of admixture, by the weight of Cement 0.45% of cement weight: 1.80 Kg

Start the Trial Again with these detail described above

Now we calculate the quantity of the material for a trail mix

1. Cement = 368 * 0.045 = 16.56 kg
2. Water = 140 * 0.045 = 6.3 kg
3. 20 mm = 642 * 0.045 = 28.89 kg
4. 12.5 mm = 636 * 0.045 = 28.62 kg
5. Sand = 808 * 0.045 = 36.36 kg
6. Admixture = 1.8 * 0.045 = 0.081 kg

Trial Mix Procedure

We are repeating the procedure because it’s very important tips for a trail mix.

1. Take the weights of all material, as described above.
2. After weighing materials, put coarse aggregates 20 mm and 12.5 mm first in the trial mix drum.
3. Now add fine aggregate ( sand ) in trial mix drum and then add the cement.
4. Mix these materials in the dry condition in a drum for at least 30 seconds.
5. Then add 80 to 90 % of the water in a drum in many parts by adding throughout the mix.
6. Add a bit more water in the mix, where you are going to add admixture.
7. Mix the remaining water with the admixture, then add admixture in a concrete mix where you added a bit more water.
8. It’s because, if the mix is fully coated with water, then it will not absorb admixture in it’s pores, and now admixture will perform his best performance.
9. Finish these steps within two minutes.
10. Check if any dry mix sticked inside the surface of a drum, instantly remove it manually from a surface by using a trowel. Stop the drum mixture for a maximum of 10 seconds for this action and restart it again.
11. Mix it for continuously 5 minutes.
12. Check the workability.
13. This is called an initial slump. Note down.
14. Don’t mix the concrete mix continuously; otherwise, the mix will produce more heat, and it causes a decrease in the slump of concrete mix.
15. Start the mixer at the 5-minute interval for about 1 minute.

Requirement of Workability

As we described, our requirement of a slump is 125 – 150 mm at the site. We have to check the slump after each 30-minute interval of up to 120 minutes ( 2 hours).

Trial Mix Cube Casting Procedure

We are repeating this because it’s very important tips for trial cube casting.

1. Cube casting shall be done just after a slump test after 2 hours.
2. Cast the concrete cubes manually for better accuracy, don’t use the plate vibrator.
3. Cast the concrete cubes by the same procedure as we usually cast.
4. Cubes shall be cast in three-layer, and each layer’s thickness is 50 mm nearly.
5. But strokes for each layer shall be between 35 to 45. No more difference for an accurate result.
6. Maintain the temperature of the lab or room where trial cubes are going to be cast at 27 +/- 2-degree centigrade.
7. After casting 12 numbers of trial cubes, place the casted cubes on a plane and firm platform. It should be a vibration-free place.
8. Place cover sheet on top of each casted cubes to prevent water evaporation.
9. Leave it for 24 hours
10. After 24 hours, de-mold the trial cubes and give the identification by a permanent marker. Do not use the nail to write on cubes.
11. Place these trial cubes in the water tank immediately, where water temperature shall be maintained at room temperature 27 +/- 2-degree centigrade.

Compressive Strength of Trial Cubes

As we described before, we cast 12 numbers of a cube for compressive strength

3 cubes for 3 days

3 cubes for 7 days

and 6 cubes for 28 days.

1. So after 3 days of casting cubes, take out three cubes from the water tank.
2. Bring these cubes to a compressive testing machine and let it dry. We should test cubes, at least in surface saturated dry conditions.
3. Before the test, the cubes set the rate of loading of the compression testing machine at 5 KN per second.
4. Place the cube carefully in the compression testing machine in the center position.
5. Start the compression testing machine and go to the ultimate load.
6. Note down the ultimate load reading.
7. Same like 3 days, we should test for 7 days and 28 days.

Required Compressive Strength for Trial Cubes

As we described before that our target means strength for M30 is 42 Mpa.

But for 3 days and 7 days, we are giving below

1. Minimum compressive strength required in 3 days – 40 % – 17 Mpa
2. Minimum compressive strength required in 7 days –  80 % – 34 Mpa

Trial Mix Result

1. Workability Result

2. Compressive Strength Result 

So as you can see from this result described above, we got a good result in 3 days, 7 days and 28 days. Average of 28 days strength is ( 42.47 + 42.5 ) / 2 = 42.49 N/mm² .

Which is greater than 42 MPa. As we described, as per MORTH 5th revision, our requirement in 28 days for M30 is 42 MPa. So now, we got the perfect proportion for the M30 grade of concrete.

FAQ: M30 Concrete Mix Design

What is M30 concrete?

M30 concrete is a specific grade of concrete defined by its compressive strength, which is targeted to be 30 megapascals (MPa) at the 28-day mark.

What are the key ingredients of M30 concrete?

The key ingredients of M30 concrete include cement, aggregates (coarse and fine), water, and sometimes admixtures. These are carefully proportioned to achieve the desired strength and workability.

How is the mix ratio determined for M30 concrete?

The mix ratio for M30 concrete is determined based on the desired strength, workability requirements, and specific conditions such as exposure and maximum aggregate size. It typically involves a combination of cement, sand, and aggregates in specific proportions.

What is the importance of trial mixes in M30 concrete design?

Trial mixes are essential to validate the proposed concrete mix design. They help assess workability, density, and most importantly, the compressive strength of the concrete at various ages. Adjustments can be made based on the trial mix results to ensure the desired performance is achieved.

How are trial mixes conducted for M30 concrete?

Trial mixes involve selecting the proposed mix proportions, conducting a slump test to assess workability, casting test cubes, and testing them for compressive strength at specified intervals (e.g., 3 days, 7 days, and 28 days). Adjustments to the mix design may be made based on the trial mix results.

What factors can influence the compressive strength of M30 concrete?

Factors influencing the compressive strength of M30 concrete include the quality and proportions of ingredients, curing conditions (temperature and moisture), mixing technique, and the presence of admixtures.

What are the acceptable strength criteria for M30 concrete?

The strength criteria for M30 concrete are typically defined by standards or project specifications. Common requirements include achieving the specified characteristic compressive strength (e.g., 30 MPa at 28 days) and meeting any additional performance criteria such as durability or workability.

How can one optimize the mix design for M30 concrete?

Mix design optimization for M30 concrete involves adjusting the proportions of ingredients, fine-tuning the water-cement ratio, and potentially incorporating admixtures to improve workability or enhance strength development. Trial mixes play a crucial role in this optimization process.